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Noise reduction scheme of brushless motor

Cross-flow fan, as one of the application fields of motor, requires low noise, stable speed and long service life of motor in many fields. These requirements can be met one by one. Here, we provide a sine wave control scheme for the noise problem. 

Cross-flow fan uses sine wave brushless motor, which overcomes the problems of small blowing range and low airflow, and also reduces noise. As for how to reduce noise, what are the advantages of sine wave brushless motor? Let's check it out.

The electronic commutation technology is adopted in the cross-flow fan brushless motor, and its essence is the structure of "flip-chip DC motor", that is, in the design of brushless motor, no brushes are implanted, permanent magnet steel is installed on the rotor side, and armature winding is installed on the stator side.

Brushless motors can be divided into BLDC and PMSM according to the differences of back electromotive force and driving current waveforms. These two differences mainly lie in the square wave type of BLDC back electromotive force and driving current waveform close to trapezoidal waveform, while permanent magnet synchronous PMSM is a sine wave type brushless motor whose back electromotive force and driving current waveform are positive selection waveform.


Brushless motor driven by square wave is very easy to control, but its noise is relatively large because of the large fluctuation of torque ripple and the difficulty of commutation. If the motor has the problem of back electromotive force, the stability of torque ripple will be worse, and the associated noise will increase significantly. If it is changed to sine wave brushless motor, the sinusoidal mode can be selected to control the torque ripple, so as to appropriately reduce the vibration frequency of the motor, thereby reducing the noise of the brushless motor of the cross-flow fan and obtaining the application performance. 

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